Ivuna meteorite

The Ivuna meteorite is a 0.7-kilogram carbonaceous chondrite (type
CI1, see below) which landed near Ivuna, Tanzania, on December 16, 1938.
It was subsequently split into a number of samples.

Ivuna was one of four meteorites, including the Orgueil
meteorite, in which Bartholomew Nagy and George Claus1 claimed
to have found evidence of primitive extraterrestrial fossils. Subsequent
analysis led to this claim being discredited. However, in 2001, investigation
by a team from the Scripps Institution of Oceanography, the Leiden Observatory
in the Netherlands, and the NASA Ames Research Center,2 showed
the presence in Ivuna of two simple amino acids, glycine and beta-alanine, and linked Ivuna with
a likely origin in the nucleus of a comet. For more on this discovery and
its implications, see the entry for the Orgueil
meteorite.

In June 2008, the largest specimen of the Ivuna meteorite was bought by
the Natural History Museum (NHM) in London from a private collector in the
US. Most of the other specimens are held by private collectors or by the
Tanzanian government. Before being put on display, the NHM's Ivuna fragment
will be taken to NASA's Johnson Space Center,
where a 20g piece will be removed and subdivided into two 10g pieces. One
of these pieces will be set aside, while the other will be further divided
into 200mg allocations for various teams of researchers to study.

What does the classification CI1 mean?

Ivuna is one of only nine known meteorites that are classified as type CI1
carbonaceous chondrites. These meteorites contain "heavy elements" (i.e.,
elements other than hydrogen and helium) in nearly the same abundances as
in the Sun, which means that they are essentially unaltered since they were
formed at about the same time as the solar system itself, some 4.6 billion
years ago. The designation CI1 indicates that Ivuna underwent a high degree
of aqueous alteration (or chemical change due to the presence of water).
This alteration took place in the parent body of the meteorite at low temperatures,
probably in the range of 20–50°C, and in a water-rich environment.
By contrast, ordinary chondrites have experienced thermal metamorphism under dry conditions in a temperature
range of 600–900°C.

CI1 type meteorites are very dark, because of their high carbon content, contain a high proportion of of iron-rich clays or phyllosilicates, and have very fine grain size. In Ivuna, there is also
a complete absence of chondrules, owing
to the fact that they have all been altered to clays and iron oxides.